Dhaka, Bangladesh — Golam Mostafa Sarder starts every day before dawn, rising from a thin reed mat in the shed that he shares with fifteen roommates. Each has just enough space to lie flat. He dresses ...

You probably don't put much thought into brushing your teeth. If you use an electric toothbrush, you assume it's getting your teeth cleaner than a manual toothbrush. However, there are better ways to ...